Hair waving lotion



United States Patent HAIR WAVING LoTroN Judson H. Sanders, Cincinnati, Ohio, assignor to The Procter & Gamble Company, Ivorydale, Cincinnati, Ohio, a corporation of Ohio No Drawing. Application February 12, 1954, Serial No. 410,027

10 Claims. (Cl. 16787.1)

The present invention relates to reducing agents for keratin, and more particularly to reducing agents possessing effective reducing power in prolonged periods of contact with keratin-containing substances without imparting undesirable damage thereto.

The use of thioglycolic acid, as a reducing agent in cold hair waving procedures is Well known. Ordinarily the thioglycolic acid is used as an aqueous solution of about 5% concentration at a pH from about 7 to about 10, usually ammoniacal to a pH of about 9 to 9 /2. While the thioglycolic acid actually exists as a salt under such conditions of alkalinity, I shall refer to it as the acid in order to simplify terminology and references to weight percentages in the description which follows.

In the reaction between keratin and thioglycolic acid the disulfide linkages which connect polypeptide chains in the keratin molecule are reduced to sulfhydryl groups, and in such reducing reaction the contact period between the keratin-containing substance and the acid must be carefully controlled in order that undesirable damage to the keratin-containing material may be avoided.

In hair waving procedures employing thioglycolic acid, the exercise of precaution in time of contact is especially important. The speed of reaction of thioglycolic acid with the keratin of the hair is dependent, among other things, on shaft diameter, porosity, chemical composition and reactivity, and the condition of the hair, as for example degree of oiliness, at the time of treatment with the keratin reducing agent. Thus the optimum time of contact with thioglycolic acid in a hair waving operation to achieve a desired degree of reduction of hair cannot be generalized. A given contact time that may be optimum for the hair of one individual may prove detrimental or otherwise unsatisfactory for the hair of another individual, the reaction proceeding at too fast or too slow a rate depending on the variables above noted, and either carrying the reduction to the point of undesirable damage or not carrying it far enough to permit desired waving.

There has been evident need for a reducing composition which will react with keratin at a satisfactory rate to produce a desired reduced keratin but which will react further to effect damage only at a greatly retarded rate once the desired reduction has been effected.

It is an object of the present invention to provide a composition having improved qualities as a keratin reducing agent. Another object is to provide a keratin reducing agent which may be employed in the treatment of keratin with high degree of safety against damage. A further object is to render thioglycolic acid less damaging to keratin-containing substances during use in the reduction of the keratin. A still further object is to provide an improved thioglycolic acid reducing composition for use in permanent hair waving operations. Another object is to provide a composition which possesses the property of materially minimizing the individual effects of the many variables entering into permanent hair waving operations in that it permits increasing the period during which the thioglycolic acid may be safely left in contact with desirably reduced keratin.

I have discovered that dithiodiglycolic acid, the disulfide of thioglycolic acid, when used in combination with thioglycolic acid in a limited range of proportions, has the characteristic of retarding undesirable reaction of thioglycolic acid to give hair damage known in the art Without at the same time affecting unfavorably the desirable reducing reaction of the acid with the keratin. The compositions of my invention in aqueous solution under the usual conditions of alkalinity known in the art may thus be effectively employed to reduce keratin with markedly greater safety against damage than has heretofore been possible. For example, 1 have found that immersion for 10 minutes at F. of human hair (a strand of 12 hairs wound on a mandrel having a diameter of 6.5 mm.) in a 5% solution of thioglycolic acid ammoniacal to about pH 9.2 containing less than 1% of dithiodiglycolic acid, followed by conventional rinsing and fixing, will effect perceptible damage to the hair, the 20% index (a measured indication of damage as determined on the Scott 1P2. Serigraph described below) being in the neighborhood of .25 as compared with 1.00 for the untreated hair, the lower 20% index figure being indicative of greater damage. The average diameter of the curl was about 7.5 mm. When test curls of the same hair were immersed, rinsed, and subsequently fixed, under comparable conditions in a 5% solution of thioglycolic acid, containing also 1.5% of dithiodiglycolic acid ammoniacal to pH 9.2, the 20% index was about 0.58 and the average curl diameter was about 7 mm. In this solution the molar ratio of dithiodiglycolic acid to thioglycolic acid was 0.15:1. An increase of the dithiodiglycolic acid content to about 3% (molar ratio=0.3:1) resulted in a marked further reduction in damage, the 20% index being about 0.75, curl diameter being about 7.7 mm.

Such protection against damage to the keratin-contaim'ng substance was apparent also when solutions containing 2%, 7.5% and 10% thioglycolic acid ammoniacal to about pH 9.2 were employed, increase in the protection as measured by 20% index being observed with increase in the molar ratio of dithiodiglycolic acid to thioglycolic acid. The protective action was also observed when immersion time of the hair in the various solutions was increased from 10 minutes to 60 minutes, these times being comparable to exposure times on the head during actual permanent waving of about 1 /2 hours and about 6 hours respectively.

The presence of dithiodiglycolic acid in hair waving lotions containing thioglycolic acid as the reducing agent is not unknown. The dithiodiglycolic acid is the disulfide of thioglycolic acid and usually occurs in small quantity as an impurity resulting from oxidation of the thioglycolic acid by contact with oxygen of the air. Heretofore, however, dithiodiglycolic acid has been considered to be harmful to the hair waving performance of thioglycolic acid and this position is supported by John F. Mulvaney, who states in his article in Proceedings of the Scientific Section of the Toilet Goods Associations for May 17, 1946, pages 3338, that the presence of more than 1% of the disulfide is harmful. As far as I am aware, efforts of the industry have been toward minimizing exposure of thioglycolic acid to the air and thereby maintaining the dithiodiglycolic acid content as low as possible.

In prior applications for U. S. Letters Patent by I ohn W. Haefele, for instance Serial Nos. 93,192 and 142,726, filed May 13, 1949 and February 6, 1950, respectively, since abandoned in favor of Serial No. 211,183, new Patent N0. 2,615,828 of October 28, 1952, for improvements in the treatment of keratin, it is proposed to react disulfide with sulfite (including bisulfite and hydrosulfite) to form organic thiosulfate and a mercaptan, the thiosulfate serving 'to inhibit the observable damaging effect of rn'ercaptans generally in the treatment of keratin-containing substances. As is pointed out in these applications, and more particularly in the later filed application, Serialv No. 142,726, the improvement thereby achieved is due primarily to the introduction of the organic group of thiosulfate, and the advantage derived by the employment of disullide alone was therefore not recognized. The instant invention, on the contrary, contemplates the "use of disu lfides in a mixture which is substantially free from reagents proposed by Haefele, namely sulfite and organic thiosulfate. I

'In accordance with my observations, the presence of dithiodiglycolic acid does reduce somewhat thespeed with which the thioglycolic acid reacts with the keratin and thereby extends somewhat the contact time necessary for desirable reduction. However, the protective action offered by the dithiodiglycolic acid against damage heretofore experienced in prolonged exposure, especially in the novel proportions hereinafter stated, more than compensates for the lowering of the reactivity. of the thioglycolic acid with unreduced keratin. In other words, with increase in dithiodiglycolic acid content of the solution the safety factor increases more rapidly than does the contact time required for adequate reduction. Thus the compositions of my invention are useful in hair waving operations with greater safety than heretofore has been possible due to the protective action imparted to the compositions by the presence of limited amounts of the reactivity controlling agent, dithiodiglycolic acid. A distinct advantage is that with marked reduced danger due to over-exposure, directions for use are more easily standardized, thereby enabling users, who for some reason cannot select a time of exposure without some danger of unsatisfactory results, to employ the reducing composition with safety and obtain an acceptable Wave with minimum damage.

The efficacy of compositions of my invention, especially as regards hair waving, cannot be evaluated accurately by damage considerations alone and overall performance is therefore determined by a series of tests involving evaluation of a number of measured characteristics of the treated hair, including curl diameter'and curl length, aswell as damage.

In the case of curl diameter a strand of 12 human hairs 4.25 inches in length and cemented at each end is Wetwound on a mandrel 6.5 mm. in diameter, then saturated for a given time at 100 F. with the keratin reducing solution. After the wound strand of hair has been exposed to the solution for the given contact time, the solution is rinsedfrom the strand which is then treated with a solution of an oxidizing agent, e. g. dilute hydrogen peroxide (2.2 volume hydrogen peroxide) or sodium perborate monohydrate, for 3 minutes to set or fix the curl. Following application of the fixing agent, the hair is again rinsed, removed from the mandrel and, while wet and without assistance from external force, is allowed to assume a circular curl which is measured for average diameter. From the information available, deficiency in tightness or D. I. T. of the curl is determined as follows:

D. I. T.=

diameter of curl (mm.) diameter of mandrel (mm.)

diameter of mandrel (mm.) X

With all variables except reducing solution held constant,

D. I. T. is of course indicative of waving efliciency of the solution. The lower the D. I. T. value, the higher the effectiveness.

Curl length is an indication of both waving efficiency of the reducing solution and damage suffered by the hair during contact with the solution. When fr'eshly:formed curls are suspended by the end and shaken up and down, the elasticity or spring of the formed coil may be observed. The degree of laxity of the spiral coil is'indicative of waving efficiency of the solution and the degree of damage effected thereby. Numerical indication of this characteristic is obtained by measuring the curl length. The longer the curl, the greater the damage, assuming of course adequate potential efiiciency in the reducing solution.

Damage caused by excessive contact of the hair with the solution is also indicated by a factor termed 20% index. In the determination of this factor, an apparatus known as the Scott IP2 Serigraph is used. This instrument is designed to record the stretch of keratincontaining fibers by the application of a uniformly increasing load. The ratio of the load required after treatment of the fibers to the load required before treatment to stretch a wet strand of 12 fibers 20% of the original length is referred to as the 20% index, the higher the index, the lower the reduction in fiber strength and hence the lower the damage. The instrument is equipped with two clamps between which the strand of 12 fibers of keratin-containing substance is mounted. The strand is surrounded by a water-saturated wicking arrangement which keeps the hair wet during stretching. One of the clamps is fixed to a bar which inclines at a uniform rate when the machine is in operation, and the other clamp is attached to 'a weighted carriage adapted to travel along the bar and away from the first mentioned clamp when the bar is inclined. As the inclination of the bar increases, the stretch load applied by the carriage increases at a uniform rate and the strand of fibers is elongated. The relation between load and elongation is continuously recorded on a chart by a pen fixed to the moving carriage. When the elongation of the strand reaches 20% of the original length between the clamps, the machine is reversed and the bar slowly and uniformly returns to horizontal position. With decrease in load the strand contracts, usually at a rate less than the rate of elongation, thereby forming a hysteresis loop on the chart. The load required to effect 20% stretch can be read from the chart.

The difficulty in making direct comparisons of curls produced under different exposure times is readily evident because in addition to the fixed variables there are a number of measured variables. For example, assume that a given reducing solution produces the following result:

Curl Exposure Time (min) Length D. I. T. 20% Index From the above table it will be observed that the 6 minute curl has the best length but that the 8 minute curl is tighter and that damage increases steadily with exposure-time. It has heretofore been difficult to choose from such results an optimum time for a given reducing solution.

In order thatva fair evaluation of the overall efiiciency of the reducing solution may be determined, a method of weighting the different measurements in order to arrive at a single quantity that permits direct comparison of results of different experiments, and especially of different series of experiments, has been established. To this end, limits of normal interest in permanent Waving studies have been set as follows:

Minimum Maximum Curl length (mm-.) 45 and below D.I. H 0... 100 Damage (as 20% Index)--. 0

Each range isdfvided'into 10 parts and the parts are assigned Partial curl values (PCV) ranging from 1 to 10, the lower partial curl values denoting more desirable characteristics. These partial curl values are shown in the following table.

I D. I. T. values over 100 are, of course, possible and in special cases, it; is useful to assign them, but, normally, curls having D. I. T. values over 100 are of no interest.

The curl value (CV) is the sum of the partial curl values for length (L), deficiency in tightness (D. I. T.), and damage (D). Obviously the best possible curl will have a curl value of 3, and the poorer the curl, the higher the curl value.

When a series of experiments is conducted with a given reducing solution at varying times of contact, it is found that the curl value gradually decreases to a minimum and then increases. The minimum point is usually clear-cut, although a good solution may stay at its minirnum curl value over an extended period of time. A curl value of 8 has been arbitrarily chosen on the basis of past experience as the maximum value indicating an acceptable curl achieved by well known and acceptable commercial reducing solutions.

The minimum curl value attainable is, of course, a measure of the quality of the solution, that is, it measures the optimum that can be achieved with the solution.

The time to reach minimum curl value is a measure of the speed of the reducing action of the solution weighted with respect to both damage and waving.

The duration of a given curl value, such as 8 or below, for example, over increasing times of contact is indicative of the effective safety period of the solution. In other words, the effective safety period is a measure of the length of time during which an acceptable curl may be obtained without danger of objectionable damage.

In the example cited above showing actual determinations for curl length, D. I. T. and 20% index, the following partial curl values and calculated curl values are noted.

was obtained after an exposure time of 7 minutes.

With the above explanations the results obtained with reducing solutions of my invention as set forth in the following examples will be readily understood. It is to be borne in mind, however, that the specific conditions given in the examples, wherein all parts shown are by weight, are merely illustrative of the broader aspects of the invention more fully covered in the appended claims.

were mixed with water and concentrated ammonium hydroxide (28% NHs) to bring the total to 100 parts and the pH to 9.3. In this solution the molar ratio of dithiodiglycolic acid to thioglycolic acid was about 0.2:1. Portions of this solution were used to produce a number of test curls of hair by exposure of individual curls for variable times. Partial curl values for length, deficiency in tightness, and damage were determined in accordance with the methods described above. The curl value of the solution of this example reached a minimum of 5 after exposure of the test curl to the solution for 10 minutes and the duration of time of exposure during which a curl value of 8 or less was obtained was about 15 minutes.

In comparison with a corresponding aqueous solution at pH 9.3 and containing a .055 mol. of thioglycolic acid per parts of solution, no dithiodiglycolic acid being used, a minimum curl value of 6 was reached after 6 minutes exposure. However, the duration of time of exposure during which curl values of 8 or less were obtained was only 3 minutes.

Example 2.-An aqueous solution similar to that of Example 1 but containing a greater proportion of dithiodiglycolic acid was prepared from 5.15 parts (.056 mol.) thioglycolic acid, 3.4 parts (.019 mol.) dithiodiglycolic acid and sufiicient water and ammonium hydroxide to bring the total to 100 parts and the pH to 9.3. The molar ratio of dithiodiglycolic acid to thioglycolic acid in this solution was about 0.33:1. This solution was tested over a range of exposure times as above described and it was found that a minimum curl value of 5 was achieved after 8 minutes exposure. The duration of time of exposure during which a curl value of 8 or less was obtained was about 31 minutes.

Example 3.An aqueous solution similar to that of Examples 1 and 2 but containing a greater proportion of disulfide was prepared from 5.15 parts (.056 mol.) thioglycolic acid, 3.95 parts (.022 mol.) of dithiodiglycolic acid and sufiicient water and ammonium hydroxide to bring the total to 100 parts and the pI-l to 9.3. The molar ratio of dithiodiglycolic acid to thioglycolic acid in this solution was about 0.39:1. A minimum curl value of 5 was obtained after 12 minutes exposure to this solution. The duration of time of exposure during which a curl value of 8 or less was obtained was longer than minutes but not as long as 450 minutes, curl values of 6 and 9 respectively being obtained after exposure for these times. By extrapolation it was estimated that the safety period or duration of a curl value of 8 or less for this solution was in the neighborhood of 400 minutes.

Example 4.An aqueous solution similar to that of Examples 1, 2 and 3 but containing a greater proportion of dithiodiglycolic acid was prepared from 5.24 parts (.057 mol.) of thioglycolic acid, 7.9 parts (.043 mol.) of dithiodiglycolic acid and suflicient water and concentrated ammonia to bring the total to 100 parts and the pH to 9.3. The molar ratio of dithiodiglycolic acid to thioglycolic acid in this composition was about 0.76:1. This solution was tested over a range of exposure times as above described and it was found that a minimum curl value of 5 was obtained after 18 minutes of exposure. The duration of time of exposure during which a curl value of 8 or less was obtained was longer than 450 minutes but not as long as 1020 minutes, curl values of 7 and 10 respectively being obtained after exposure for these times. By extrapolation it was estimated that the safety period for this lotion was in the neighborhood of 500 minutes.

Examination of the waving performance of other keratin-reducing compositions containing substantially higher molar ratios of dithiodiglycolic acid to thioglycolic acid than those covered by the above examples indicated that the effective safety period decreased from a maximum reached around a molar ratio of 0.8:1, the decrease being due to a lowering of the quality of the reducing solution so that a curl value of 8 or less was obtained over a shorter period of time. Thus the effective safety period for a molar ratio of 1.5 :1 was about 90 minutes and at a molar ratio of 3.2: 1, a very poor quality reducing solution with a minimum curl value of only 10 was obtained. It is evident therefore that for the purposes of the present of dithiodiglycolic acid present invention, the amount zyrregsre 7 relative to the thioglycolic acid is a significant factor, the protective action of the dithiodiglycolic acid being readily demonstrable between molar ratios of 0.15:1 toabout 1.521 but being outstanding and of particular value between molarratios of about 0.25:1 to about 0.8:1.

In the above examples I have shown that the compositions of my-iriv'ention may be prepared by mere compounding of the essential ingredients. However, since dithiodiglycolic acid is a disulfide resulting from the oxidation 'of thioglycolic acid, the compositions of the invention can be-prepared by the controlled oxidation of a thioglycolic acid solutionas more fully illustrated in the following examples.

Exc'zm'ple 5.6.7 parts of thioglycolic acid, which was substantially free from dithiodiglycolic acid, were dissolved in 70 parts water and the solution was made alkaline by the addition of 4.6 parts of ammonium hydroxide containing 28% NHs. To this solution were added 3.2 parts of a 10% solution of hydrogenperoxide, 1.7 parts of thioglycolic'acid being oxidized to about 1.7 parts dithiodiglycolic acid. Caution was exercised to keep the solution cool during oxidation. The resulting solutioncontainingdithiodiglycolic acid and thioglycolic acid in the molar ratio-of about 0.17:1 was then adjusted to 100 parts and a pH of 9.3 by the addition of water and ammonia. The mixture showed good quality waving performance, adequate speedof reducing action and an effective safety period substantially above that of a comparable thioglycolic acid solution containing substantially no dithiodiglycolic acid.

Example 6.66.5 parts of commercial ammonium thioglycolate containing the equivalent of 33.8 parts thioglycolic acid and 1.2 parts dithiodiglycolic acid were mixed with 396.46 parts water and the mixture was'm'ade alkaline by the addition of 19.55 parts ammonium hydroxide (28% NHs). To the mixture were added 6.24 parts of commercial 26.35% hydroxide forming about 10.5 parts of ammonium dithiodiglycolate which is equivalent to about 8.9 parts of dithiodiglycolic acid. The production of 8.9 parts dithiodiglycolic acid consumed about 9.0 parts thioglycolic acid. The resulting mixture therefore contained the equivalent of about 10.1 parts dithiodiglycolic acid and 24.8 parts of thioglycolic acid. To the mixture was added 11.24 parts of an'op'acifying agent comprising mineral oil, oleic acid and potassium oleate. The composition contained the equivalent of about 5% thioglycolic acid and had a molar ratio of dithiodiglycolic acid to thioglycolic acid of 0.2:1. The pH of the mixture was 9.3.

When the performance of this composition was tested as a hair waving agent substantially in the manner described above, an exposure time of minutes being'used, the following results were obtained:

Curl diameter=7.8 mm. Curl length=40+ mm. 20% index=0.61

These results indicate good performance, the curl value of the solution being 8.

Example 7.7.0 parts (.076 mol) of thioglycolic acid, and 7.9 parts (0.043 mol) dithiodiglycolic acid were mixed with water and concentrated ammonium hydroxide (28% NHs) to bring the total to 100 parts and the pH to 8.6. In this solution the molar ratio of dithiodiglycolic acid to thioglycolic acid was about 0.57:1. This solution was tested at exposure times of 7, 10 and 60 minutes, a curl value of 8 being obtained after the 60 minute exposure time. Similar tests with a comparable solution containing no dithiodiglycolic acid, but otherwise the same, resulted in greater damage to the hair at each of the three exposure times, and in no instance was a curlvalue of 8 or less obtained.

Example 8.3.'5 parts of thioglycolic acid, and 3.95 parts of dithiodiglycolic acid were mixed with water and concentrated ammonium hydroxide as in Example 7 to bn'ngthe-total'to 100 parts and the pH to 10.0. The concentrations of dithiodiglycolic acid and thioglycolic acid were one-half those of the solution employed in Example 7 but the molar ratio was the same. The solution was tested at exposure times of 7, 10 and minutes, curl values less than 8 being noted after both the 7 and 10 minute exposure times. Similar tests with a comparable solution containing no dithiodiglycolic acid, but otherwise the same,- resulted in much greater damage to the hair at each of the exposure times, and in no instance was a curl value of 8 or less obtained. In fact, omission of the dithiodiglycolic acid resulted in badly damaged hair after 7 minutes exposure.

In-the above-examples the solutions were made alkaline by the addition of ammonia, it being well known that solutions of mercaptans which have been rendered al kaline by-the addition of ammonia are superior to comparable solutions which have been rendered alkaline by the addition of. other alkalizing materials such as alkali metal'carbonates and hydroxides including sodium and potassium carbonates and hydroxides. The superiority exhibits itself primarily in the lower destructive action which ammoniacalsolutions have toward the keratin-containing substance. In the practice of the present invention the advantageous protective action demonstrated above in connection with ammoniacal solutions is also observed in the case of solutions rendered alkaline by the addition of alkali metal'hydroxides or carbonates or mixtures thereof with ammonia; thus the invention may be of slightl'ygreater advantage in the use of these latter solutions. Other alkalizing agents including watersoluble amines, such as ethyl amine, monoethanolamine and morpholi'ne, and also water-soluble quaternary ammonium bases such as tetraethyl ammonium hydroxide can be used. All ofthese alkaline agents, and mixture thereof, may be substituted for the ammonium hydroxide employedin the foregoing examples, in appropriate quantities', with generally comparable results.

In conventional lotions containing thioglycolic acid as the active ingredient, the alkalinity is customarily controlled between pH 9 and pH 9 /2, usually pH 9.2 to 9.3. Experience has taught that such alkalinities are conducive to a good wave in a minimum of time with a minimum of hair damage. This range of alkalinity is also preferred for'usein the practice of the present invention, but it is to be understood that the protective action of the dithiodiglycolic acid is evident at alkalinities which are lower than pH 9 and higher than pH 9 /2. Thus, although waving efficiency tends to decrease with decrease in alkalinity, lotions having an alkalinity as low as pH 8 /2 have utility in the art, and, as shown by Example 7, the protective action of the dithiodiglycolic acid is quite evident and can be used to advantage in waving lotions of such lower alkalinity.

It must be borne in mind that in the waving of hair under normal home-use conditions with a lotion which has been alkalized -with ammonia, care must be exercised to prevent appreciable loss'of ammonia by volatilization and concomitant reduction of pH substantially below Lotions having 'alkalinities anound pH 8 /2 have little reserve ammonia to protect against such loss and accordingly it is preferable to use a buifering agent, such as ammonium carbonate, to maintain the desired pH. Under the exacting conditions of laboratory control, however, loss of ammonia through volatilization can be prevented and desired pH values maintained throughout the waving period without resorting to the use of buffering compounds.

The protective properties of the dithiodiglycolic acid are of even greater value in waving lotions which have pH values higher than 9 /2 and, as Example 8 shows, waving lotions having alkalinities as high as pH 10 can be used without undesirable damage to the hair.

In effect, therefore, the use of the present invention minimizes the'need for the customarily practiced rigid control of the alkalinity within the range pH 9 and pH 9 /2 and enables the production of practical and safe-touse waving lotions having pH values from about 8 /2 to about 10.

Thioglycolic acid, even when employed in combination with dithiodiglycolic acid as protective agent, is more rapid in its waving action at higher alkalinities than at lower alkalinities in the range of about pH 8 /2 to about pH 10, and the tendency to damage the hair follows this same pattern. Such difierences in activity can be compensated for, either by varying the time of exposure or by varying the concentration of active ingredients inversely with the pH value. In practice, an eifort is made to employ an exposure time which is fixed within a rather narrow range, thereby reducing the need for judgment on the part of the user to a minimum, and it is preferable that concentration be varied inversely with pH value. Thus, the concentration of thioglycolic acid within the range of about 2% to about and the pH of the solution within the range of about pH 8 /2 to about pH 10 are preferably adjusted so as to obtain in a given time of exposure a permanent change in the configuration of the hair without damage thereto, the concentration being in the higher portion of said concentration range for a lower pH and in the lower portion of said concentration range for a higher pH. It will be appreciated, however, that increases in concentration at pH values from 9 /2 to 10 are accompanied by greater tendency toward damage than are corresponding increases in concentration at pH values from 8 /2 to 9. In the conventional range of pH 9 to pH 9 the concentration of thioglycolic acid is preferably controlled from about 4% to about 6%, the actual concentration depending on whether the waving lotion is designed for use on hard-to-wave or easy-towave hair.

While the essential ingredients of the compositions of my invention include thioglycolic acid and dithiodiglycolic acid, it is to be understood that other ingredients such as perfume, opacifying agents, buffers and other ingredients to impart desired qualities to the reducing solution may be incorporated without departing from the spirit of the invention.

This application is a continuation-in-part of my copending application Serial No. 193,540, filed November 1, 1950 and now abandoned.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. A hair waving lotion for effectively waving hair without imparting undesirable damage thereto, comprising essentially an aqueous solution of a mixture of thioglycolic acid and dithiodiglycolic acid substantially free from sulfite and organic thiosulfate, the concentration of thioglycolic acid in solution being from about 2% to about 10%, the molar ratio of dithiodiglycolic acid to thioglycolic acid being from about 0.15:1 to about 1.5:1, and the alkalinity of the solution being from about pH 8.5

to about pH 10, said concentration and alkalinity being adjusted within said ranges so as to obtain in a given time of exposure a permanent change in the configuration of the hair without undesirable damage thereto.

2. A hair waving lotion in accordance with claim 1 in which the solution is ammoniacal to about pH 8.5 to about pH 10.

3. A hair waving lotion in accordance with claim 1 in which the pH range is from about pH 9 to about pH 9.5.

4. A hair waving lotion in accordance with claim 1 in which the concentration of thioglycolic acid is of the order of 5%, the alkalinity being adjusted from about pH 9 to about pH 9.5 by the presence of monoethanolamine.

5. A hair waving lotion in accordance with claim 1, adjusted in pH by the presence of monoethanolamine.

6. A hair waving lotion in accordance with claim 5 in which the pH is from about pH 9 to about pH 9.5.

7. A hair waving lotion in accordance with claim 1 in which the molar ratio range is from about 0.25:1 to 0.8:1.

8. A hair waving lotion in accordance with claim 7 in which the pH range is from about pH 9 to about pH 9.5.

9. A hair waving lotion in accordance with claim 7 in which the solution is ammoniacal to a pH from about 9 to about 9.5.

10. A hair waving lotion for effectively waving hair without imparting undesirable damage thereto, comprising essentially an aqueous solution of a mixture of thioglycolic acid and dithiodiglycolic acid substantially free from sulfite and organic thiosulfate, the amount of thioglycolic acid in solution being of the order of 5%, the molar ratio of dithiodiglycolic acid to thioglycolic acid being from about 0.25 :1 to 0.821, and the solution being ammoniacal to a pH of about 9 to 9.5.

References Cited in the file of this patent UNITED STATES PATENTS Haefele Oct. 28, 1952 OTHER REFERENCES Mulvaney, Proc. Sci. Sec. Toilet Goods Assn, May 17, 1946, pp. 33-38, especially p. 37.

Draize et al., The Percutaneous Toxicity of Thioglycolates, The Toilet Goods Assn., No. 7, May 16, 1947, pp. 29-31.

Michaelis, A Study of Keratin, J. Am. Leather Chemists Assn., vol. 30, 1935, pp. 557-568, p. 562 esp. pertinent.

Bersin, Chem. Abstracts, vol. 32, 1938, pp. 5283-4.

.Dahle et al., Methods of Analyzing Cold Wave Solutions, The Am. Perfumer & Essential Oil Review, Feb. 1945, pp. 35-38.

Reed et aL, Permanent Waving of Human Hair: The presented before the Boston Meeting of for the Advancement of Science, Dec. 26,

Cold Process, the Am. Assn. 1946, 10 pp. 

1. A HAIR WAVING LOTION FOR EFFECTIVELY WAVING HAIR WITHOUT IMPARTING UNDESIRABLE DAMAGE THERETO, COMPRISING ESSENTIALLY AN AQUEOUS SOLUTION OF A MIXTURE OF THIOGLYCOLIC ACID AND DITHIODIGLYCOLIC ACID SUBSTANTIALLY FREE FROM SULFITE AND ORGANIC THIOSULFATE, THE CONCENTRATION OF THIOGLYCOLIC ACID IN SOLUTION BEING FROM ABOUT 2% TO ABOUT 10%, THE MOLAR RATIO OF DITHIODIGLYCOLIC ACID TO THIOGLYCOLIC ACID BEING FROM ABOUT 0.15:1 TO ABOUT 1.5:1, AND THE ALKALINITY OF THE SOLUTION BEING FROM ABOUT PH 8.5 TO ABOUT PH 10, SAID CONCENTRATION AND ALKALINITY BEING ADJUSTED WITHIN SAID RANGES SO AS TO OBTAIN IN A GIVEN TIME OF EXPOSURE A PERMANENT CHANGE IN THE CONFIGURATION OF THE HAIR WITHOUT UNDESIRABLE DAMAGE THERETO. 